1. Field of the Invention
The present invention relates generally to semiconductor packages and, more particularly, to a quad flat package (QFP) which is uniquely configured to provide increased signal processing capability without an increase in size as a result of the inclusion of one or more internal semiconductor packages.
2. Description of the Related Art
One of the most commonly used semiconductor packages in the electronics industry is referred to as a quad flat package (QFP). A typical QFP includes a die pad or paddle which has a quadrangular configuration and is located at the approximate center of the package. Arranged along all four sides of the die paddle in spaced relation thereto is a plurality of leads. A semiconductor die is attached to the die paddle, and is electrically connected to the leads through the use of conductive wires. The semiconductor die, the die paddle, the leads and the conductive wires are encapsulated by an encapsulant which, upon hardening, forms a package body of the package. Typically, the leads protrude from respective ones of four sides of the package body, and are each bent so as to have a gull-wing configuration. These leads are used to mount the QFP to an external device. Quad flat packages having the above-defined structural attributes are manufactured through the use of processes which are relatively simple, and thus cost efficient.
However, one of the primary drawbacks in quad flat packages as currently known is that many of the leads arranged about the periphery of the die paddle must be used for grounding or power supply. As a result, difficulties often arise in ensuring a sufficient number of leads available for signal transfer. Due to known restrictions associated with the chemical etching or mechanical stamping process employed in manufacturing the die paddle and leads of the quad flat package, an increase in the number of leads results in a significant increase in the overall size of the package. As will be recognized, an increase in the size of the package in turn requires a larger area for the mounting thereof to an external device, thus making it more difficult to mount the package in small electronic appliances or devices such as cellular phones, personal digital assistants, and portable notebook computers.
Also known in the electronics industry are various techniques for stacking semiconductor packages upon each other in a manner achieving a desired pattern of electrical interconnection between the semiconductor dies of the stacked packages. Though package-to package stacks provide benefits of increased signal processing and transfer capability, they are often difficult to use in small electronic appliances or devices due to their relatively large thickness. Additionally, there are typically limitations in the number of packages that may be stacked upon each other in a package-to-package stack, with the pattern design of the printed circuit boards for accommodating the stack often becoming complicated, and the package stack itself being relatively costly to manufacture.
The present invention provides a quad flat package or QFP type semiconductor package which provides an increased number of leads for signal transfer without the penalty of increased package size. The increased signal transfer capability is provided by employing principles of stacking internally within the package. These, as well as other attributes and advantages of the present invention, will be described in more detail below.